Opalescent glass and method of making same



Patented Feb. 5, .1946

ormsonm' omss AND Mn'rnon or MAKING am worm Weyland Norbert a. Kreidl. State Collose, Pa assiznors to Monsanto-Chemical Gompony. a corporation of Delaware No Drawinx. Application September 10, 1941.

. Serial No. 410.292

6 Claims. (Cl. 106-63) ous shapes without the development 01 suriace defects such as roughness, etc.

It is another object to provide an opal glass composition which will not crystallize during working or molding.

Opal glasses have been known and produced for a great many years. At the presentitime such opal glasses are generally produced by the incorporation of cryolite oroi sodium silico fluoride in 13111;:L glass melt, making what is known as a fluoride o Etill earlier it was the practice, before the discovery oi fluoride Opals, to employ bone ash as an opacifying agent in glass. Bone ash opacifled glasses however were generally unsatisfactory and hence upon the discovery of fluorine opals they were gradually superseded by the latter type of glass. The replacement of the bone ash opals by the fluoride opals is generally believed to be due to the fact that the bone ash opals exhibited an undesirable tendency to develop surface deiects such as roughness which is now believed to be due to excessive crystal growth during cooling.

We have now found that the opaciiying agent in the earlier bone ash opal glasses was partly. hydroxy apatite, and that the prior defects were formula above assures I the hydroiry apatite due to the iormation oi this substance as a part 01 v the opacifying phase. l I

Bone ash when free of organic materials contains approximately the following amounts of the various constituents:

7 Percent 'lrlcalcium phosphate B4 'irimagnesium phosphate A 2 Calcinm carbonate 10 alcium fluoride 4 From the above analysis it will be noted that v.

bone ash generally contains a small amount of fluorine. However. it is important to note for the understanding or the present invention that the amount oi calcium fluoride present is insufllcient to form fluorapatite with the calcium or other divalent elements and P201; present so that there was always some hydroxyapatite present.

Men of typical fluorapatite opal glasses according Y to our invention.

' Example 1 Mix together the following ingredients and melt f ace: in a glass. urn Pounds Sand (S102) 260 Barium boro silicate 18.5 Barium carbonate 7.5

Borax (NaeBaO'z 10H20) s Limestone (CaCOs) 17.5 Nephelin Syenite 75.5 Tetrasodium pyrophosphate '75 Sodium nitra' 8 Sodium carbonate u 65 Litharg 22.0 Fluorspar 33.0 Arsenic trioxide 3.0

In the above composition the phosphorus hearing salt is supplied as tetrasodium pyrophosphate, which as is noted will supply sufllcient oi the phosphorus pentoxide together with an appreciable amount of the soda necessary.

It is, of course, possible to supply the PiOsnecessariLv present; as any other suitable salt of phosphorus. The following composition illustrates the use of a very pure form or apatite which supplies calcium, P 01; and fluorine to the glass body. 7

Example 2 Pounds. Sand (8102) 259.5 Barium boro silicate--. 18.5

. Borax (NaiBzOv 101-120) 4 Barium carbonate 7.5 Nephelln Syenite '15 'I'etrasodiummyrophos'phate; ..e.. 61.0 Sodium nitrate 8.0 Sodium carbonate 72.5 Litharge 22.0 Fluorspar A 32.0 Apatite 19.0 Arsen 3 We have now round that a much more satisiactory opaciflcation or glass may be obtained it the composition of the glass is so adjusted that it' contains an excess 01 fluorine over that necessary to produce the mineral fluorapatite which has the formula: 8CauPO0aCaFa- The employment or .1% of iron.- The-above down and molded into an excess oi fluorine over that called for by the that all or the calcium phosphate is present as the fluorapatite and that shall be substantially absent.- The following examples illustrate the produc- The apatite hereirr added is a mineral of very high purity containing less than approximately ingredients are melted glassware for various purposes.

ides are equally useful.

In the table below we give three eramples'oi fluorapatite opal glasses employing our invention and in the fourth column we give the prererred range or the constituents which are therein em-= played:

Composition of glam Preferred Constituent we Per cent Per cent Per cent Per rem SiOs 59 88. 8 d2 3 54-66 A1301; 8 8. 31 5.0. -6

i6 i5. 8 l4 Iii-l7 5 (i. 2 l0 0-12 5 1.8 0 H 6 6.0 0 'M 3 3. 0 4. 0 & 5-6 0 75 0 (a) 0 L 0 0 0-1 6 7. 25 5. 0 4-9 I In borosilicate glasses less. 8 From 0 to about 60 in borosilioete glasses.

In general the following? considerations gov= cm the range of constituents shown in the table above.

Silica is, of course, employed since it is a con= venient and cheap glass forming mineral. content should not be increased above that shown, since high viscosities are encountered which make workability dimcult.

Some A120: is desirably incorporated in our fluorapatite opal glass and is useful for extending smaller concentrations of'the opacifier, i. e. of

aerator tions as the fiuorapatite opal glasses by P205" and F.

Percent $103 55.8 A130: NasO-l-Kz I; 15,3 CaO v I 6.2 Hat) P190 to F at 'EgO-i 55 A 0; 1.00 P205 the working range of the glass and also for avoidins devitriflcation. It moreover prevents attack upon refractories and decreases the amount of opaciflers employed.

Sodium and potassium should be restricted to the amount necessary for fiuxing since excessive amounts interfere with fluorapatite opacification. Qther alkali metals such as lithium should be absent because of the strong fiuxing eflect oi this element. The present invention isto be distin= suished from the opal glasses which have been produced using such minerals as amblygonitea lithium containing mineral-where the opaci=- iication is produced by gaseous silicon fluoride.

CaO, 32.0 and PM) as a group are necessary for opacification since they enter into the opacifying phase by the formation of apatite bodies or bodies consisting of partially substituted apatite containing apatite. However, not all of these on Lime is the preferred and cheapest material to employ since it enters into the production of fiuorapatite 3as(P104)z.CaFt

Barium oxide and lead omde decrease the crystal formation and growth particularly in the desir able working range or temperature.

Boric oxide is introduced and may be employed in rather wide amounts since it is useful for controlling the heat resistance or the finer-apatite 'opal glass. It is desirably employed in a low alkali content glass. The low refractive index of the borosilicate glass and the high refractive index of fluorapatite cause the fluorapatite opal glassesto be more easily opacified than the fluorine opal glassea'whenever boron ispresent in high amounts, because the refractive index of sodium and calcium fluoride is low.

Both fluorine and P205 are employed in the Y ranges indicated and preferably substantially in the indicated ratio. Fluorapatite opalescent classes can be produced by analogous prepare- Pounds Sand (SiOa) v 259.5 5 Barium borosilicate 18.5 Borax (NmBaOrJOHzO) 4.0 Barium carbonate 7.5 Nepheiin Syenite 75.0 'I'etrasodium pyrophosphate 61-.0 7 Sodium nitrat 8.0 Sodium carbonate 72.5 Litharge 22.0 Fiuorspar 32.0 Apatite 19.0 8.0

78 Arsenic stantially as follows:

What we claim is: 1. An opal or opalescent glassware composition having a calculated oxide content which is substantially as follows;

Percent Sim '59 Mad)! 3 New +&O 15 @gn 5 33,0 5 P12 5 4 r 3 P205 5 2. An opal or opalesoent glassware compontion having a calculated oxide content whichis substantially as follows: r

. l p 3. An opal or opalescent glassware composition having a calculated oxide content whichis sub- Percent S102 62 Alana 5 Nero-{ & 14 Cat) 16 F a0 P205 59 e. An opal or opalescent glassware making 5. An opal or opalescent glassware making batch having substantially the following composi tion: 

